Galaxy Note 4 lags when on voice call.

I have noticed that my Samsung Galaxy Note 4 seriously lags when I'm on a phone or voice call. I'm normally unable to multi-task. Ie, surfing the Internet or Google searches during a voice call. It takes too long for the Stock browser or Chrome to load.

I have upgraded from Note 2 and recently discovered I had this issue which did not even appear in the older model.